1. Field of the Invention
The present invention relates to a method of manufacturing a thermal head.
2. Description of the Related Art
There has been conventionally known a method of manufacturing a thermal head for use in thermal printers (see, for example, Japanese Patent Application Laid-open No. 2010-94939). In the method of manufacturing a thermal head described in Japanese Patent Application Laid-open No. 2010-94939, a concave portion is formed in one surface of an upper substrate, and a support substrate is bonded onto the upper substrate so as to close the concave portion. After that, heating resistors are formed on a rear surface of the upper substrate in a region opposed to the concave portion, and then the rear surface is covered by a protective film, to thereby manufacture a thermal head which has a cavity portion between the upper substrate and the support substrate.
In the thermal head manufactured in this way, the cavity portion functions as a heat-insulating layer of low thermal conductivity to reduce an amount of heat transferring from the heating resistors toward the support substrate side via the upper substrate, to thereby increase an amount of heat to be utilized for printing and increase heating efficiency. The heating efficiency is determined by dimensions of the concave portion, a thickness dimension of the upper substrate, resistances of the heating resistors, a thickness dimension of the protective film, and the like. It is therefore required to reduce fluctuations in such dimensions.
However, in the manufacturing process for a thermal head, the above-mentioned dimensions, resistances, and the like fluctuate among the substrates or lots. Further, the concave portion and the upper substrate are disposed under the heating resistors, the electrodes, the protective film, and the like, and hence the dimensions cannot be measured or corrected at a final stage after the thermal head is assembled. Therefore, the conventional manufacturing method has a problem that fluctuations in heating efficiency cannot be suppressed and it is difficult to manufacture a thermal head having stable quality.